As a batch type apparatus which performs a vacuum process such as a film forming process on a semiconductor wafer (hereinafter, referred to as a “wafer”), there is known a vertical heat treatment apparatus including a wafer boat in which a plurality of wafers are stacked in the form of shelves, and a reaction tube (reaction vessel) which is formed of quartz and into which the wafer boat is airtightly inserted from the bottom thereof. For example, on the side surface of the reaction tube, one end portion of an exhaust port formed of quartz to vacuum-evacuate the reaction tube is thermally bonded to the reaction tube, and the other end portion of the exhaust port is connected to an exhaust pipe made of metal and extending toward a vacuum pump. An end portion of the exhaust pipe on the side of the exhaust port is fixed to, e.g., a housing forming an outer casing of the apparatus such that although an inner atmosphere of the reaction tube is set to be a vacuum atmosphere, the exhaust pipe is not pulled (moved) toward the atmosphere. Further, in order that a peripheral portion of a lower end portion of the reaction tube is in airtight contact with an upper surface of a lid installed at a lower end portion of the wafer boat in a circumferential direction, the reaction tube is fixed to a base plate while being maintained horizontally from the lower surface side thereof by a bottom flange serving as a ring-shaped attachment member at a position lower than a position at which the wafers are stacked in the wafer boat. Accordingly, a positional relationship between the position at which the end portion of the exhaust port on the side of the exhaust pipe is fixed and the position at which the lower end portion of the reaction tube is fixed is approximately determined in the apparatus.
When mounting the reaction tube on the apparatus or exchanging the reaction tube, the reaction tube is fixed to the bottom flange while the bottom flange is moved down, and then the bottom flange is fixed to the base plate while the bottom flange is moved up such that the other end portion of the exhaust port faces the open end portion of the exhaust pipe. Subsequently, for example, an operator airtightly connects the exhaust port with the exhaust pipe using a flange member for piping. Accordingly, the reaction tube is airtightly connected to the exhaust pipe.
However, since a quartz product has poor fabricability compared to, e.g., a metal material, the quartz product may have low fabrication accuracy. Accordingly, a length dimension of the exhaust port, a direction of the exhaust port extending from the reaction tube, or the like may be changed for each reaction tube. Since a positional relationship between the exhaust pipe and the lower end portion (bottom flange) of the reaction tube is determined in the apparatus as described above, when connecting the exhaust port to the exhaust pipe, excessive force may be applied to the exhaust port, thereby causing breakage of the reaction tube in the thermally bonded portion between the exhaust port and the reaction tube.
The exhaust pipe is divided into a first pipe on the side of the exhaust port and a second pipe on the side of the vacuum pump, and a certain amount of margin is provided in a bolt hole in which a member for fixing the first pipe to the housing, e.g., a bolt, is inserted. Further, the first pipe and the second pipe are airtightly connected to each other by a bendable, expansible and contractible bellows such that a fixing position of the first pipe can be adjusted according to the posture of the exhaust port. However, since a fixing operation of the first pipe or the exhaust port is performed at a higher position (over the head of an operator), the exhaust port may be fixed at a deviated position with respect to the exhaust pipe, and similarly, an excessive force may be applied to the exhaust port. In this case, although a position deviation of the exhaust pipe with respect to the exhaust port is very small, since the thermally bonded portion of the reaction tube and the exhaust port is spaced from the fixing position, the exhaust port may be further deviated from its position as it goes to the thermally bonded portion, thereby applying a large force to the thermally bonded portion. Further, when there is a very large dimensional error of the reaction tube or the exhaust port, even though the above-described margin is provided, it may be impossible to absorb the dimensional error, and excessive force may be applied to the exhaust port.
Meanwhile, for example, when the above-mentioned bellows is installed between the first pipe and the exhaust port such that the bellows can move according to the position of the exhaust port, the bellows is contracted when a vacuum atmosphere is set in the reaction tube. Accordingly, the exhaust port is pulled toward the exhaust pipe and the exhaust port may be deviated from the reaction tube (broken). Although a vertical heat treatment apparatus is known as a conventional technology, the above-described problem has not been addressed.
The objective of the present disclosure is to provide a vacuum processing apparatus and an assembly method of the vacuum processing apparatus which includes a reaction vessel made of quartz to prevent the breakage of the reaction vessel.